1. Field of the Invention
The present invention relates to an image reading device of the so-called sheet-through type in which a document image is read from one main surface side of a transparent document glass, while the document that is the object of reading is conveyed so as to move on the other main surface of the document glass, and to an image forming apparatus equipped with the image reading device.
2. Description of the Related Art
In an image forming apparatus such as a copier, in a case where a document image is read with a sheet-through image reading device and the image is printed, a stripe-like image extending along the sub-scanning direction sometimes appears in the image. This stripe-like image is usually a result of contamination caused by adhesion of foreign matter such as dirt, dust, or paper powder from the conveyed document to the glass (document glass) of the image reading device. Because this stripe-like image appears as a black stripe on the white background of recording paper after printing or as a white stripe in the image zone, a document reading device has been suggested in which, as indicated in Japanese Patent No. 3313098, in a case where the stripe-like image is detected, the document reading position of a scanner provided in the image reading device is moved in the sub-scanning direction, the document is read in a position without the dirt or the like, and the user is warned when the scanner position is changed. Further, as described in Japanese Patent Application Laid-open No. 2006-148677, an image reading device has been suggested in which the contaminated portion on the document glass is lighted and displayed in the illumination mechanism of a scanner and the user is asked to clean the document glass.